Apparatus for treating paper stock



March 8, 1955 E. cowLEs 2,703,533

APPARATUS FOR TREATING PAPERv s'rocx Filed April s, 1952 5 sheets-sheet1 s 1o 15 2o 25 30 35 aw/,7 Bw/e5 ATTORNEYS AMarch 8, 1955 E. cowLEsAPPARATUS PoR TREATING PAPER sTocx Filed April 3, 1952 5 Sheets-Sheet 2INVEN-ron faw//l Cow/es BY 47,247@ 2P ATTORNEYS March 8, 1955 E. cowLEsAPPARATUS FOR TREATING PAPER STOCK 5 Sheets-Sheet 3 Filed April 3, 1952INVENTOR.

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ATTORNEYS March 8, 1955 E. cowLEs 2,703,533

APPARATUS PoR TREATING PAPER sfrocx Filed April 5, 1952 s sheets-sheet 4HryT/o ATTORNEYS March 8, 1955 E. COWLES APPARATUS FOR TREATING PAPER.STOCK Filed April 3. 1952 5 Sheets-Sheet 5 ATTORNEY United States PatentO 2,703,533 APPARATUS FOR TREATING PAPER STOCK. Edwin Cowles, Cayuga, N.Y., assignor to The Cowes Company, Princeton, N. J., a corporation ofNew Jersey Application April 3, 1952, Serial No. 280,256 12 Claims. (Cl.92-26) This invention relates to apparatus for treating paper stock.

This application is filed as a continuation in part of my copendingapplications Serial No. 137,743, tiled January l0, 1950, and Serial No.252,930, filed October 24. 1951, both now abandoned.

ln the preparation of paper stock for delivery to a paper makingmachine, it is desirable, in most cases. to subject the stock to threetypes of action, ("1) a pulping and debering action to separate theindividual fibers one from another, (2) a hydrating and fbrillatingaction which brushes and frays the fibers while at the same time causingthem to absorb water, and (3) a cutting action to reduce the fibers tothe desired length. It is necessary to completely defiber the stockinall cases, but in making certain types of paper, the cutting action orthe hydrating and fibrillating action may be minimized, and one type ofaction may be caused to predominate over the other. ln fact, one of theskills of the paper making art is the ability to prescribe and obtainthe type and degree of action required to produce paper of the desiredproperties and characteristics. 4

lt is an object of the present invention to provide apparatus which iscapable of producing an unusual degree and type of fibrillating action,thereby producing an unusual strength development in the finished sheet.I

It is a further object of the invention to provide apparatus in whichthis unusual degree and type of fibrillating action can be produced inless time and with the consumption of less power than is ordinarilyrequired to produce a lesser action.

It is a further object of the invention to provideapparatus in whichthis unusual degree and type of fibrillating action may be produced witha minimum of concomitant cutting of the fibers, thus permitting greatstrength development with only very slight accompanying loss in tearstrength.

lt is a further object of the invention to provide apparatus which maybe easily and quickly adjusted to produce an action which is eitherpredominantly a hydrating and fibrillating action, or which ispredominantly a cutting action.

It is a further object of the invention to provide apparatus in which ahighly eicient defibering action always accompanies the refining actionof the apparatus irrespective of whether the apparatus is adjusted forhydration and fibrillations or for cutting. This defibering action isaccomplished without any substantial increase in the power consumptionrequired to hydrate, fibrillate and cut the stock.

Finally, therefore, it is an object of the invention to provideapparatus which will accept raw, undefibered stock, and in which suchstock may be defibered, and may be simultaneously hydrated, tibrillatedand/or cut as desired by the operator, with power consumption which doesnot exceed that which could be required to produce comparable hydration,fibrillation and/or cutting alone in the same apparatus, and with powerconsumption substantially less than required to produce comparablehydration, fibrillation and/or cutting alone in refining apparatus suchas a Hollander beater or a Jordan engine of the prior art.

Other objects and advantages of the invention will appear hereinafter.

A preferred embodiment of the invention selected for purposes ofillustration is shown in the accompanying drawings, in which,

Figure 1 is top plan view of the apparatus.

Figure 2 is a vertical section on the line 2 2 of Figure 1.

Figure 3 is an enlarged view of the front face of the.

rotor and bedplate.

Figure 4 is a vertical section on the line 4 4 of Figure 2.

Figure 5 is a section on the line 5 5 of Figure 4.

, Figure 6 is a front elevation of a knife.

Figures 7, 8 and 9 are sections through the knife on the lines 7 7, 8 8and 9 9 of Figure 6.

Figures 10, l1 and 12 are similar sections through a knife of modifiedform.I

Figure 13 is a section on the line 13 13 of Figure 2.

Figure 14 is a diagram showing typical results obtained by the use ofthis apparatus while maintaining constant pressure between the knivesand bedplate.

Figure 15 is a similar diagram showing typical results obtained whenpressures are increased during the treatment of the stock.

Referring to the drawings, the operating unit (apart from the container,tank or enclosure in which it is mounted) is shown in detail in Figures3, 4 and 5, and comprises a bedplate 1 and a rotor 2 carrying knives 3.In the preferred embodiment illustrated, the bedplate is in the form ofan annular ring having a working surface provided with a multiplicity ofalternating grooves 4 and bars or lands 5.

The rotor 2 is mounted on shaft 6 for rotation therewith. The tangs 7 ofknives 3 are clamped firmly to the rotor 2 by a ring 8 having bolts 9extending through the tangs and into the rotor. The knives extendoutwardly from the rotor and are in contact with the bars 5 of thebedplate. It is preferred that the leading edges of the knives 3 shouldengage the bars and grooves of the bedplate at a slight angle, andaccordingly in the `embodiment illustrated in which the bars and groovesare arranged substantially radially, the knives are set so that theleading edges cross the bars and grooves at an angle between 10 and 30.

The knives are so constructed that during the operation of the machinethe motion of the knives relative to the bedplate produces a hydraulicreaction which holds the knives in yielding contact with the.bedplate.Referring to Figures 6, 7, 8 and 9, it will be observed that the undersurface of each knife is recessed at 10, leaving only a relativelynarrowfoot 11 extending along the leading edge and in contact with thebedplate bars. As shown in these figures, the upper surface l2 of theknife, immediately adjacent the advancing edge 13 intersects the bottomsurface of the foot at a relatively small angle, preferably less thanforty-five degrees, which has been found to be a favorable angle forcausing fibers to be picked up and retained on the advancing edge.Preferably the advancing edge of the knife is rather sharp and if themetal of the surface 12 s hardened, the knife will tend to be selfsharpening in use. The remainder of the upper surface 14 is curvedsmoothly and intersects the surface 10 to form the trailing edge 15 ofthe knife. The knife is tapered toward its outer tip, resulting in crosssections of progressively decreasing area as shown in Figures 7, 8 and9. In all sections, however, the width of the knife is substantiallygreater than its thickness.

A modified form of knife 3l is shown in Figures l0, 11 and 12 whichwould show slightly better hydraulic efficiency, but which would be morefragile and more costly. The form shown in Figures 7, 8 and 9 representsa practical departure from the theoretically more efficient form ofFigures 10, l1 and 12 made in the interest of added strength anddecreased cost. In both forms, the motion of the knives relative to thebedplate produces a hydraulic reaction having two distinct aspects.First, a region of reduced pressure is created within the space 16between the surface 10 and the bedplate which tends to draw the twotogether to hold the knives in yielding contact with the bedplate.Second, the motion of the knives causes the stock to exert a downwardpressure on the upper surface of the knife. The combination of reducedpressure on the under side of the knife and increased pressure on theupper side is particularly effective in maintaining yielding contactnear the outer tip of the knife due to the fact that in practice the tipof the knife is moving at a relatively high speed, as for example at3000' per min. or more. It is also particularly important near the outertip of the knife for the knife is not completely rigid and has atendency to flex. The

combination of hydraulic pressures aids in maintaining effective contactthroughout the length of the knife.

lt is desirable that the bedplate and the rotor be mounted for relativeaxial movement, and in the embodiment illustrated, the rotor is fixed inits bearing housing but the bedplate is movable axially relative to therotor. Thus the bedplate is mounted on three push rods 17 which aremounted in and guided by sleeves 18. Said rods are connected to a collar19 which, in turn, is connected to three hydraulic cylinders 20.. Saidcylinders are connected to a source of hydraulic pressure by pipes 21having a pressure regulator 22 therein through ,which the pressure inthe cylinders may be controlled.

A rubber gasket 23 may be interposed between the bedplate and thecasing. Since the bedplate of the embodiment illustrated is a closedbedplate (having no slots or apertures extending therethrough) thereduced pressures within the spaces 16 under the blades tend to draw thebedplate toward the knives and to hold it against the knives with ayielding pressure of some magnitude. This pressure may be increased (ordecreased if desired) by varying the pressure applied to the cylinders20.

The nature of the refining action on the fibers, that is, whether ahydrating and fibrillating action predominates or whether a cuttingaction predominates, is determined primarily by the pressure between theknives and the bars of the bedplate. In general, even when using rathersharp knives, when light or moderate pressures are applied, as when thehydraulic reaction above described are relied upon alone, or when suchhydraulic reactions are supplemented by moderate additional pressuresfrom the cylinders, a hydrating and fibrillating action will predominatewith little or no cutting of the fibers. If, however, pressures areincreased substantially, and even assuming no change in the sharpness ofthe knives, a cutting action will predominate. Increased sharpness ofknives will, of course, increase somewhat the cutting effect obtained atany given pressure.

The nature of the refining action is inuenced importantly by the spacingbetween successive bars of the bedplate. It will be understood that thewider the spacing between successive bars, the further a knife must movebetween successive engagements, and the greater the opportunity for theknife to pick up fibers. Thus, if the spacing between successive bars(i. e. groove width) is l, a knife would be likely to pick up twice asmany fibers as if the spacing was y As a result of extendedexperimentation and close observation of such machines under variousconditions, I am convinced that the very unusual results which have beenrecorded as to extraordinary strength development (tensile and Mullenburst test) accompanied by unusually low loss of freeness and unusuallylow loss of tear strength, are due in large part to the use of abedplate in which the bars are very closely spaced. If the spacingbetween successive bars (i. e. groove width) is less than 1/2" itappears that at ordinary operating stock consistencies of 4% to 6% aknife tends to pick up only a few fibers constituting more or less asingle layer of fibers, while at spacings greater than this, a pad4 offibers is likely to be accumulated. With only a few fibers it appearsthat subsequent engagement with a bar causes the individual fibers to bedragged across the edges of the knife causing the walls and ends of eachfiber to be torn and frayed, whereas with an accumulation of sufficientfibers to form a pad, it appears that some of the fibers are protectedfrom such fraying action. In any event, I have observed that withincreased bar spacing the loss of tear strength is more pronounced, andthe development of tensile and burst strength (Mullen) proceeds moreslowly. I prefer to limit the space between the bars, therefore, to l/"or less, for in this way I obtain results which it is difficult, if notimpossible, to duplicate in any existing apparatus.

l have obtained excellent results with a bedplate in which the distancebetween adjacent bars (groove width) is 366". In this bedplate, asillustrated in Figures 7 to l2 inclusive, the depth of' the grooves is1;/4" and the width of the bars varies from %5" at their inner ends to1A" at their outer ends. However, the depth of the grooves and the widthof the bars do not appear to have important significance, as it appearsto be the groove width alone which affects the character of the resultson the bers.

The unusual results obtained in my machine are shown in Figures 14 andl5 showing curves plotted from tests on pulp treated in my machine.

The pulp selected for the test.recorded in Figure I4 was a bleachedTacoma kraft pulp `in water at 68 F. at a consistency of 4.5%. Theentire charge of pulp was introduced in to the machine in the form ofair dry sheets at the beginning of the run. Samples were taken atregular intervals and tested by accepted standard procedures. Theresults are plotted in terms of horsepower per ton per day.

During the test, the pressure between the knives and bedplate wasconstant and relatively low, the pressures induced by the hydraulicreaction of the knives being only slightly supplemented by pressureapplied by the hydraulic cylinders. During the operation of themachine,the stock was defibered as well as hydrated and fibrillated, but becauseof the low pressures between the knives and bedplate, there was verylittle cutting. The curves indicate a moderate but steady increase inMullen strength which was still increasing at 35 horsepower per ton perday when the test was discontinued. This was accompanied by a rapidincrease in tear strength up to about l2 horsepower per ton per day,followed by a relatively slow decrease in tear strength. Simultaneously,a gradual and relatively slow drop in freeness was observed.

Ordinarily, a paper maker would discontinue treatment far short of 35horsepower per ton per day, and the significance of the results shown bythese curves is that for any given Mullen strength which may berequired, stock treated in my machine will in almost every case show ahigher tear strength and a smaller drop in freeness than will the samestock treated in standard equipment such as a Hollander beater or aJordan engine to obtain a Mullen strength of equal value. For example, asimilar stock treated in a Hollander beater to produce a Mullen strengthof 80% (reached in my machine at l5 horsepower per ton per day) wouldshow lower tear strength and a greater freeness drop than those hererecorded.

The pulp selected for the test recorded in Figure l5 was a WeyerhaeuserStandard Bleached Sulphite Pulp in water at F. at a consistency of 5%.Again the entire charge of pulp was introduced into the machine at thebeginning of the run in the form of air dry sheets. Samples were takenand the results plotted in the same manner as before.

In this test, the pressure between the knives and bedplate was increasedgreatly at approximately 9.5 horsepower per ton per day, the outsidepressure applied by the hydrauliccylinders having been increased fromapproximately 6 lbs. per square inch to approximately 50 lbs. per squareinch 'at this point. The effects of the increased pressure are showngraphically in the curves. Thus, the tensile curve turns upwardly quitesharply and the Mullen curve also turns upwardly, but less sharply. Onthe other hand the tear curve and the freeness curve,

' both of which were tending to level off at 9.5 horsepower per ton perday, again turn downwardly. This test was discontinued at 25 horsepowerper ton per day, but the qualities shown by these tests at any valuebetween l0 and 25 horsepower per ton per day are unique in their highMullen and tensile strengths with the accompanying tear and freenessreadings. These qualities are often sought but have seldom beenachieved. They are believed to be largely due to the unusual type anddegree of fibrillation which is obtained in the ordinary use of mymachine with relatively sharp knives.

In making certain types of paper, however, greater hydration and lessfibrillation is sometimes required. In such cases, this may beaccomplished in my machine merely by using knives having a dull ratherthan a sharp advancing edge. In such case, there is less tendency tofray the fibers and more tendency to crush and pound them. Preferably,however, the machine is equipped and adjusted as previously described.

The importance of these results is further increased by the fact that inthese tests the pulp was supplied in the form of air dry pulp sheets.Ordinarily the defibering treatment of the stock required to prepare itfor refining treatment would require the expenditure of approximately 2to 5 additional horsepower per ton per day, whereas in my machinedebering proceeds coincidentally with the refining.

The detibering action in my machine is extremely efcient although itsexact nature is not yet completely understood. It is believed to' resultfrom a combination of mechanical and hydraulic forces working on theUndoubtedly some defibering results from the direct mechanical action ofthe -knives working against the bedplate. Then again, an area of extremeturbulence exists in the spaces 16 beneath the knives which probablyproduces a combined hydraulic and mechanical deliberng action therein.This would be augmented, no doubt, by an area of turbulence lyingimmediately behind the trailing edge 15 of each knife in which ahydraulic deibering action might be irected. It suffices vto say thatthe delibering action is s ciently rapid and ellicien't to be completedprior to the time when the required rening action has been completed,and with no appreciable increase in power consumption. That is, theresults obtained after expenditure of any given amount of power will besubstantially the same irrespective of whether the pulp is supplied inthe form of dry sheets, or in par'- tially or completely defibered form.

In the preferred embodiment illustrated, therefore, the operatingunitpreviously described is shown as mounted in a tank capable ofreceiving raw, dry pulp, for important savings, not only in power but intime, can be achieved by thus making it possible for deibering andrefining to proceed simultaneously. Thus, the operating unit, includingthe shaft bearing housing 25 and the hydraulic cylinders 20, both ofwhich are connected to plate 26, is mounted on the at side wall 27 ofthe tank 28 with the bedplate and knives freely exposed to the contentsof the tank.

The tank is of modified cylindrical contour in which the at side wall 27is tangent to a curved wall section 29 which merges with another curvedsection 30 of somewhat longer radius. The latter meets and joins thewall 27 to form a corner 31. The operating unit is located near thiscorner.

Rotation of the rotor causes stock to be discharged outwardly in alldirections'from the axis of rotation, and in order to control thedischarge to produce adequate circulation of the stock in the tank, therotor is partially surl rounded by a casing 32, preferably of voluteform which intercepts and redirects the stock discharged from a portionof the rotor to cause it to move in the general direction of the stockdischarged from the -remainder of the rotor. The resulting circulationis somewhat as indicated by the arrows in Figures 1 and 2. A portion ofthe stock is permitted to discharge substantially vertically upwardly,as indicated, to be intercepted and dellected by the baille 33 to aid insubmerging any pieces of stock which tend to oat on the surface. Thebottom portion 34 of the casing 32 may be provided with apertures 3.5through which finished stock may be extracted. The exterior portion ofcasing 32 is surrounded by an outescasing 36 having a sump 37 and anoutlet opening If desired, the circulating action of the rotor may beincreased by mounting a series of .vanes 39 on the ring 8, said vanesbeing inclined to the radius, as shown, to

assist the normal outward discharge from the blades. A.

vane 39 on the shaft 6 may also be used to assist circulation, andparticularly to break up accumulations of pulp around the center of therotor. Such vanes assist in delibering undebered stockbut have noappreciable tecbin producing either fibrillation or shortening of e ers.

In the normal operation of the machine, the desired4 quantity of waterwill be introduced and the necessary quantity of pulp will then beintroduced to produce the desired stock consistency. In most cases, aconsistency of 4% to 6% will be advisable. One of the advantages of themachine is its ability to receive an entire charge of dry pulp at onetime. Whole bales of dry pulp may be introduced without separation ofindividual sheets or laps. In the preferred method of operation where itis desired to effect maximum strength development, the machine is thenoperated with the knives first exerting relatively light pressureagainst the bedplate. Subsequently, at a point which will be determinedby the l. qualities desired, increased pressure is applied topproducesuicient cutting for good sheet formation.

It will be understood that the invention may be variously modified andembodied Within the scope of the subjoined claims.

I claim as my invention: l. Apparatus for treating paper stockcomprising, in

' combination, a bedplate having a working surface comprising spacedbars, a rotor mounted concentrically of said bedplate, a knife carriedby said rotor, said knife `engaging the bars of the bedplate, saidtrailing edge bein g located above and out of contact with saidbedplate, said knife beingrecessed behind said foot and between saidfoot and said trailing edge to form a space between the knife and thebedplate.

2. Apparatus as claimed in claim l in which said knife is somewhatflexible and in which one end of the knife is free and the hydraulicreaction of the knife on the stock causes said knife to flex and toexert yielding pressure on said bedplate.

3. Apparatus as claimed in claim 1 in which said leading edge is formedby surfaces which intersect at an angle of less than 45 4. Apparatus asclaimed in claim l in which said bedplate and rotor are relativelymovable in a direction parallel to the axis of rotation of the rotor,and in which the hydraulic reaction produced by rotation of said rotorexerts yielding pressure between the rotor and bedplate.

5. Apparatus as claimed in claim l in which said bedplate is closed andis mounted for movement parallel to the axis of rotation of the rotor,and in which the hydraulic reaction produced by rotation of said rotorcauses said bedplate to exert yielding pressure against said rotor.

6. Apparatus as claimed in claim 1 in which said bedplate and rotor arerelatively movable in a direction parallel to the axis of rotation ofthe rotor, and in which means are provided for applying variableyielding pressure therebetween.

7. Apparatus as claimed in claim l in which said bedplate and rotor arerelatively movable in a direction parallel to the axis of rotation ofthe rotor, and in which the hydraulic reaction produced by rotation ofsaid rotor exerts yielding pressure between said rotor and bedplate, andin which means are provided for applying supplemental variable yieldingpressure therebetween.

8. Apparatus as claimed in claim l in which said bedplate is closed andis in the form of a disk and in which grooves between the bars extendradially outwardly from the center of said disk.

9. Apparatus as claimed in claim l in which the spaces betweensuccessive bars are less than'l/" in width.

l0. Apparatus as claimed in claim 1 in which said bedplate is mounted inthe wall of a tank adapted to receive raw, undebered stock, with theworking surface of said bedplate and said knives freely exposed to thecontents of the tank.

1l. Apparatus as claimed in claim-l in which said bedplate is mounted inthe wall of a tank adapted to receive raw, undefbered stock, with theworking surface of said bedplate and said knives freely exposed to thecontents of the tank, and vanes on said rotor to supplement the normaloutward discharge of stock from said rotor.-

l2. In an apparatus for treating paper stock, a knife comprising ablade'and a tang, said tang extending lengthwise from said blade at oneend thereof, said blade having a leading edge and a free trailing edge,said leading edge being formed by the intersection of two surfaces, oneof said surfaces constituting the bottom surface of a relatively narrowfooty/ extending along said leading edge, the bottom of said blade beingrecessed behind said foot and between said foot and said trailing edge,the upper surface of said blade being smoothly and convexly curved fromsaid foot to said trailing edge, and said trailing edge lying above theplane of the bottom vsurface of said foot.

References Cited in the file of this patent UNITED STATES PATENTS232,460 Cooke et al. Sept. 21, 1880 2,220,677 Cowles Nov. 5, 19402,399,988 Cowles May 7, 1946 2,527,772 Stapley et al. Oct. 31, 19502,561,013 Coghill et a1. July 17, 1951 FOREIGN PATENTS 262,070 GreatBritain May 19, 1927

